<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>demo</title>
  </head>
  <body>
    <h1>哈哈</h1>
    <button>按钮1</button><button>按钮2</button><button>按钮3</button><button>按钮4</button
    ><button>按钮5</button>

    <script>
      const foo = () => {
        console.log('foo');
      }

      console.log(foo.prototype); // undefined

      const f = new foo() // TypeError: foo is not a constructor

    </script>
  </body>
</html>
